Carboxy phosphonate pharmaceutical composition

ABSTRACT

Certain carboxy phosphonate materials affect carbohydrate metabolism.

BACKGROUND OF THE INVENTION

The present invention relates to compositions and processes for affecting carbohydrate metabolism. More specifically, certain carboxy phosphonates are administered to humans and lower animals to desirably influence carbohydrate metabolism. In particular, the compositions and processes herein are especially useful for affecting the metabolism of glucose and are useful in the treatment of diabetes.

SUMMARY OF THE INVENTION

The present invention encompasses a method for promoting the metabolism of carbohydrates, especially glucose, in humans and lower animals comprising administering to a human or lower animal in need of such treatment a safe and effective amount of a pharmaceutically acceptable carboxy phosphonate of the type described more fully hereinafter.

By the practice of this invention, disease states involving decreased metabolism of carbohydrates, especially glucose, are effectively treated. Accordingly, the present invention provides an effective means for the treatment of diabetes (diabetes mellitus).

SUMMARY OF THE INVENTION

The present invention encompasses a process for desirably affecting the metabolism of carbohydrates, especially glucose, comprising administering to a human or lower animal in need of such treatment a safe and effective amount of a pharmaceutically acceptable carboxy phosphonate material of the type described more fully hereinafter.

The present invention provides a means for treating disease states involving decreased metabolism of carbohydrates, especially glucose, and thus provides a means for treating diabetes mellitus which comprises administering to a human suffering from diabetes mellitus a safe and effective amount of a pharmaceutically acceptable carboxy phosphonate compound.

DISCUSSION OF RELATED REFERENCES

Various phosphonate compounds are reported in the literature as being useful in the treatment of anomalous mobilization and deposition of calcium phosphate salts (bone mineral) in humans and other animals. See especially the U.S. Patents of M. D. Francis: U.S. Pat. Nos. 3,683,080, granted Aug. 8, 1972; 3,678,164, granted July 18, 1972; 3,662,066, granted May 9, 1972; 3,553,314, granted Jan. 5, 1971; 3,553,315, granted Jan. 5, 1971; 3,584,124, (specifically teaching carboxy phosphonates for this use), granted June 8, 1971; 3,584,125, granted June 8, 1971; and 3,641,246, granted Feb. 8, 1972; as well as German DT No. 2360-798 (June 26, 1975); German DT No. 2343-146 (Mar. 6, 1975); and Belgian BE 822-929 (Dec. 6, 1973).

In contrast with the prior art disclosures of the use of phosphonate materials to prevent the formation of anomalous, calcified mineral deposits in bones, joints and soft tissues, the present invention is based on the new discovery that certain, select phosphonates unexpectedly and importantly affect carbohydrate metabolism at the cellular level.

The copending application of Felix and Fleisch, entitled PHOSPHONATE PHARMACEUTICAL COMPOSITION, Ser. No. 792,946, filed May 2, 1977, discloses the use of certain alkyl geminal diphosphonates to desirably affect glucose metabolism.

DETAILED DESCRIPTION OF THE INVENTION

The treatment regimens of this invention employ a safe and effective amount of a pharmaceutically acceptable carboxy phosphonate compound. These compounds are administered to treat diseases involving carbohydrate metabolism in humans and lower animals in need of such treatment.

By "safe and effective amount of carboxy phosphonate compound" herein is meant sufficient carboxy phosphonate compound to desirably affect carbohydrate (especially glucose) metabolism, at a reasonable benefit/risk ratio attendant with any medical treatment. Within the scope of sound medical judgment, the dosage of carboxy phosphonate compound will vary with the particular condition being treated, the severity of the condition, the duration of the treatment, the specific carboxy phosphonate compound employed, and like considerations as disclosed more fully hereinafter.

By "pharmaceutically acceptable" herein is meant that the carboxy phosphonate drug compound and other ingredients used in the compositions employed herein are suitable for use in contact with the tissues of humans and lower animals without undue toxicity, irritation, allergic response, and the like, commensurate with a reasonable benefit/risk ratio.

The term "administration" of the carboxy phosphonate compounds and compositions herein includes systemic use, as by injection (especially parenterally), intravenous infusion, suppositories and oral administration thereof.

By the term "comprising" as used herein is meant that various other, compatible drugs and medicaments, as well as inert ingredients, can be conjointly employed in the compositions and processes of this invention, as long as the critical carboxy phosphonate compounds are used in the manner disclosed. The term "comprising" thus encompasses and includes the more restrictive terms "consisting of" and "consisting essentially of" which characterize the use of the essential carboxy phosphonate compounds in the practice of this invention.

By "compatible" herein is meant that the components of the compositions which can be used in the practice of this invention are capable of being commingled without interacting in a manner which would substantially decrease the efficacy of the carboxy phosphonate compositions under ordinary use situations.

All percentages herein are by weight, unless otherwise specified.

The carboxy phosphonate compounds used in the practice of this invention are of the formula ##STR1## wherein, in both the vicinal and geminal carboxy phosphonates R₁ and R₂ are selected from the substituents carboxyl, hydrocarbyl, amino, hydroxyl, alkoxyl, halogen (especially chloro) providing that at least one, preferably both, R₁ and R₂ are carboxyl; R₃ and R₄ can be hydrogen, hydrocarbyl, hydroxyl, amino, alkoxyl, halogen (especially chloro); and M is hydrogen, a pharmaceutically acceptable cation, e.g., alkali metal, especially Na or K, or an alkyl or aryl moiety, e.g., methyl, ethyl, propyl, butyl, phenyl, etc. The term "hydrocarbyl" as used herein includes alkyl, unsaturated alkyl and substituted alkyl groups.

The phosphonate compounds employed herein are all known in the art and can be prepared by the general procedures described in U.S. Pat. No. 3,562,166, Nicholson, et al., Feb. 9, 1971, and U.S. Pat. No. 3,584,124, Francis, June 8, 1971, the disclosures of which are incorporated herein by reference, as well as by procedures described in Pudovik, "Soviet Research on Organo-Phosphorus Compounds," 1949-1956, Part III, 547-85c. See also the multi-volume series ORGANIC PHOSPHORUS COMPOUNDS, Kosalopoff and Maier, and references cited therein, for complete reaction sequences which can be used to prepare compounds of the type employed herein.

The gist of the present invention is the discovery that carboxy phosphonates, even short-chain carboxy phosphonates, desirably and unexpectedly affect glucose metabolism in a manner not seen with other short-chain phosphonates which do not have the carboxyl substituent, e.g., ethane-1-hydroxy-1,1-diphosphonate, methane diphosphonate, dichloromethane diphosphonate, and the like.

Carboxy phosphonates are readily dissolved in water or gastric juices and are suitable for oral administration. Preferred carboxy phosphonate compounds herein are those wherein R₁ and R₂ are each carboxyl and R₃ and R₄ are each hydrogen or hydroxyl. The vicinal carboxy phosphonate compounds are preferred over the geminal and, of the vicinal compounds, the vic-dicarboxy, vic-diphosphonates are preferred. Especially preferred herein are the ethane-1,2-dicarboxy-1,2-diphosphonates. As will be seen from the results of the cell culture experiments hereinafter, the carboxy phosphonates cause an increase in glucose consumption (and a concomitant increase in lactate production) to a level which is as much as 1.5-fold greater than that of control cell cultures.

The following experiments demonstrate the heretofore unsuspected utility of the carboxy phosphonate compounds for desirably affecting the metabolism of glucose. In the experiments, the term "MEM" means Minimum Essential Medium (Gibco); the meanings of all other terms and abbreviations are defined or are apparent from the text.

Methods Cell Culture

Calvariae of 1-day old Wistar rats were used. After decapitation the heads were kept for 1 hour in cold MEM with low NaHCO₃ (227 mg/l) containing 100 units penicillin, 100 mcg streptomycin, 0.25 mcg fungizone and 100 mcg mycostasin per ml, to kill bacteria and especially fungi found on rats. The calvariae were dissected and cleaned. 12-15 Calvariae were shaken for 2 hours at 37° C. in a 25 ml Erlenmeyer flask containing 4 ml MEM with 227 mg/l NaHCO₃, 100 units/ml penicillin, 100 mcg/ml streptomycin, 0.25 mcg/ml fungizone (= antibiotica) and 3 mg/ml collagenase (Worthington CLS II). The free cells were then harvested and plated in costar culture dishes 3524, 16 mm diameter (Tecnomara AG, Zurich, Switzerland) at a density of 40,000 cells per dish. Each dish contained 0.5 ml MEM with 10% fetal calf serum, 2.2 g/l NaHCO₃ and antibiotics and was incubated at 37° C. at 5% CO₂. The next day new medium with or without diphosphonates was added. This medium was then replaced every third day. On day 7 new medium was added and incubated for 16 hours in order to measure the lactate production and the glucose consumption. After the incubation the cells were released from the plate and counted.

Determination of Cell Number

After the media were removed, 0.25 ml of a mixture of 5 parts Hank's solution without CaCl₂, and 1 part MEM with 2.2 g/l NaHCO₃, containing 0.025% trypsin (Gibco) and 1 mg/ml collagenase (Worthington CLS II) was added to the monolayer and incubated for 3 hours at 37° C. at 5% CO₂. The cells were then suspended in 50 ml Hank's solution and counted on a Coulter Counter Model Industrial D, Coulter Counter Electronic Ltd., Dunstable, Beds, England.

Determination of Glucose and Lactate

Glucose was determined using hexokinase and glucose 6-phosphate dehydrogenase; for the lactate determination lactate dehydrogenase was used.

Expression of Results

Dodecane-1-hydroxy-1,1-diphosphonate and nonanediphosphonate at 0.25 mM induced death of the cells. Therefore they were used at a concentration of 0.025 mM. C₄ H₃ O₁₀ P₂ Na₅ (A) and also to some degree ethane-1-amino-1,1-diphosphonate precipitated in the medium at 0.25 mM, but compound (A) did not precipitate at 0.025 mM. According to some observations it appeared that cells cultured in the presence of 0.25 mM of compound (A) and 0.025 of ethane-1-amino-1,1-diphosphonate were not so easily released from the dish by collagenase-trypsin digestion as other cells.

The cell number, the lactate production and the glucose consumption given as percentage of the control are shown in Tables I, II and III. The lowest cell number was found in the presence of diphosphonates with an aliphatic side group and also with Cl₂ MDP. The lactate production and glucose consumption was most strongly reduced by diphosphonates which contained electrophilic groups. On the other hand, compounds with an aliphatic side group increased the lactate production and the glucose consumption.

In Tables I, II and III, the abbreviated terms have the following meanings: PPi is inorganic pyrophosphate; Cl₂ MDP is dichloromethane diphosphonate; ABDP is amino butane-1,1-diphosphonate; PAMDP is phenylamino-methane diphosphonate; EADP is ethane-1-amino-1,1-diphosphonate; McHDP is methane-1-hydroxy-1-cyclohexyl-1,1-diphosphonate; MDP is methanediphosphonate; and DMAMDP is dimethylaminomethane-diphosphonate.

As can be seen from the data in Tables II and III, a typical carboxy phosphonate of the type disclosed hereinabove (C₄ H₃ O₁₀ P₂ Na₅ -pentasodium ethane-1,2-dicarboxy-1,2-diphosphonate -- "EtCDP,Na₅ ") substantially increases glucose metabolism over other, short-chain non-carboxy phosphonates tested.

                  Table 1                                                          ______________________________________                                         Effect of Diphosphonates on Cell Number                                                                     Average                                                          Concentration Percentage                                         Compound      mM            of Control                                        ______________________________________                                         C.sub.5 H.sub.2 O.sub.6 P.sub.2 F.sub.6 Na.sub.2                                              0.25          116.2/94.2                                        C.sub.4 H.sub.3 O.sub.10 P.sub.2 Na.sub.5                                                     0.25          73.4                                              C.sub.4 H.sub.3 O.sub.10 P.sub.2 Na.sub.5                                                     0.025         87.7/80.6                                         CH.sub.4 O.sub.7 P.sub.2 Na.sub.2                                                             0.25          94.4/61.9                                         C.sub.5 H.sub.14 O.sub.6 P.sub.2                                                              0.25          86.0/69.8                                         C.sub.12 H.sub.28 O.sub.7 P.sub.2                                                             0.025         56.4/49.0                                         C.sub.9 H.sub.20 O.sub.6 P.sub.2 Na.sub.2                                                     0.025         57.6                                              CO.sub.7 P.sub.2 Na.sub.4                                                                     0.25          86.8/69.9                                         CH.sub.4 O.sub.8 P.sub.2 Na.sub.2                                                             0.25          80.2/62.4                                         C.sub.11 H.sub.23 O.sub.7 P.sub.2 Na                                                          0.025         42.2                                              PPi            0.25          112.5/100.9                                       PPi            0.1           93.9                                              Cl.sub.2 MDP   0.25          48.4                                              Cl.sub.2 MDP   0.025         87.6                                              ABDP           0.25          78.1                                              PAMDP          0.25          101.9/88.7                                        EADP           0.25          49.0                                              McHDP          0.25          31.8                                              MPP            0.25          84.5                                              DMAMDP         0.25          107.1/89.5                                        ______________________________________                                    

                  Table 11                                                         ______________________________________                                         Lactate Production per 10.sup.6 Cells                                                                       Average                                                          Concentration Percentage                                         Compound      mM            of Control                                        ______________________________________                                         C.sub.5 H.sub.2 O.sub.6 P.sub.2 F.sub.6 Na.sub.2                                              0.25          96.6/91.3                                         C.sub.4 H.sub.3 O.sub.10 P.sub.2 Na.sub.5                                                     0.25          155.0                                             C.sub.4 H.sub.3 O.sub.10 P.sub.2 Na.sub.5                                                     0.025         118/126                                           CH.sub.4 O.sub.7 P.sub.2 Na.sub.2                                                             0.25          32.0/22.7                                         C.sub.5 H.sub.14 O.sub.6 P.sub.2                                                              0.25          101.6/97.4                                        C.sub.12 H.sub.28 O.sub.7 P.sub.2                                                             0.025         327.1/201.5                                       C.sub.9 H.sub.20 O.sub.6 P.sub.2 Na.sub.2                                                     0.025         153.6                                             CO.sub.7 P.sub.2 Na.sub.4                                                                     0.25          53.5/40.3                                         CH.sub.4 O.sub.8 P.sub.2 Na.sub.2                                                             0.25          67.1/51.6                                         C.sub.11 H.sub.23 O.sub.7 P.sub.2 Na                                                          0.025         312                                               PPi            0.25          89.4/77.3                                         PPi            0.1           91.7                                              Cl.sub.2 MDP   0.25          33.1                                              Cl.sub.2 MDP   0.025         60.6                                              ABDP           0.25          152.3                                             PAMDP          0.25          88.5/108.3                                        EADP           0.25          160.9                                             McHDP          0.25          254.0                                             MDP            0.25          89.8                                              DMAMDP         0.25          88.2/106.6                                        ______________________________________                                    

                  Table III                                                        ______________________________________                                         Glucose Consumption per 10.sup.6 Cells                                                                       Average                                                         Concentration Percentage                                         Compound      mM            of Control                                        ______________________________________                                         C.sub.5 H.sub.2 O.sub.6 P.sub.2 F.sub.6 Na.sub.2                                              0.25          95.0/109.3                                        C.sub.4 H.sub.3 O.sub.10 P.sub.2 Na.sub.5                                                     0.25          152.0                                             C.sub.4 H.sub.3 O.sub.10 P.sub.2 Na.sub.5                                                     0.025         136.3/86.4                                        CH.sub.4 O.sub.7 P.sub.2 Na.sub.2                                                             0.25          18.0/49.6                                         C.sub.5 H.sub.14 O.sub.6 P.sub.2                                                              0.25          88.5/110.3                                        C.sub.12 H.sub.28 O.sub.7 P.sub.2                                                             0.025         306.2/197.6                                       C.sub.9 H.sub.hd 20 O.sub.6 P.sub.2 Na.sub.2                                                  0.025         153.5                                             CO.sub.7 P.sub.2 Na.sub.4                                                                     0.25          38.3/55.6                                         CH.sub.4 O.sub.8 P.sub.2 Na Na.sub.2                                                          0.25          50.9/63.8                                         C.sub.11 H.sub.23 O.sub.7 P.sub.2 Na                                                          0.025         279                                               PPi            0.25          91.2/90.7                                         PPi            0.1           116.5                                             Cl.sub.2 MDP   0.25          43.9                                              Cl.sub.2 MDP   0.025         70.4                                              ABDP           0.25          142.9                                             PAMDP          0.25          96.0/70.1                                         EADP           0.25          118.9                                             McHDP          0.25          172.6                                             MDP            0.25          91.9                                              DMAMOP         0.25          94.1/112.5                                        ______________________________________                                    

PREFERRED MODE

Within the scope of sound medical judgment, the dosage of the carboxy phosphonates herein will vary with the particular condition being treated, the severity of the condition, the duration of treatment, and like factors within the specific knowledge and expertise of the attending physician. However, single dosages can typically range from 0.01 to 500 mg per kilogram of body weight, preferably 0.5 to 50 mg/kg (unless otherwise specified, the unit designated "mg/kg" as used herein refers to mg/kg of body weight). The higher dosages within this range are usually required in the case of oral administration because of somewhat limited absorption of the carboxy phosphonates through the gut. Up to four dosages per day can be used routinely, but this can be varied to the needs of the patient, consistent with a sound benefit/risk ratio. Dosages greater than about 500 mg/kg may produce untoward symptoms and are usually avoided; moreover, daily dosages greater than about 2,000 mg/kg are not ordinarily required to produce the desired benefit and may produce toxic side effects. Again, however, patient-to-patient variations in response may be expected. Dosages of about 0.01 mg/kg are useful, especially if administered intravenously.

Preferably, dosages ranging from about 10 to about 100 mg/kg are employed when the carboxy phosphonates are administered orally, since absorption is not total.

For parenteral administration (s.c., i.p., i.m.), carboxy phosphonate dosages are preferably from about 0.5 mg/kg/day to about 20 mg/kg/day. For long-term parenteral infusion (i.v.) the most highly preferred dosage range is from about 0.5 mg/kg/day to about 5 mg/kg/day.

For purposes of oral administration the carboxy phosphonates can be formulated in the form of capsules, tablets or granules. For treatment of non-human animals, the carboxy phosphonates are preferably incorporated in animal feed, feed supplements or feed concentrates. They can also be prepared in unit dosage form together with a pharmaceutical carrier, each unit dosage form containing from ca. 15 mg to 10 g of carboxy phosphonate. The preferred concentration range of carboxy phosphonate in unit dosage forms intended for use by humans and smaller domesticated animals is from 15 mg to 1000 mg, more preferably 100 mg to 500 mg. A higher concentration range, i.e., from 1 g to 5 g is preferred in unit dosage forms intended for treatment of larger animals such as cattle, horses, etc.

As used herein, the term "pharmaceutical carrier" denotes a solid or liquid filler diluent or encapsulating substance. Some examples of the substances which can serve as pharmaceutical carriers are sugars such as lactose, glucose and sucrose; starches such as corn starch and potato starch; cellulose and its derivatives, such as sodium carboxymethylcellulose, ethylcellulose, cellulose acetate; powdered tragacanth; malt; gelatin; talc; stearic acid; magnesium stearate; calcium sulfate; vegetable oils, such as peanut oil, cottonseed oil, sesame oil, olive oil, corn oil and oil of theobroma; polyols such as propylene glycol, glycerin, sorbitol, mannitol, and polyethylene glycol; agar; alginic acid; pyrogen-free water; isotonic saline; and phosphate buffer solutions, as well as other non-toxic compatible substances used in pharmaceutical formulations. Wetting agents and lubricants such as sodium lauryl sulfate, as well as coloring agents, flavoring agents and preservatives can also be present. Tableting is done using conventional techniques.

The pharmaceutical carrier employed in conjunction with the carboxy phosphonates is used at a concentration sufficient to provide a practical size to dosage relationship. Preferably, the pharmaceutical carrier comprises from about 0.1 to 99% by weight of the total composition.

Animal feed compositions to which the carboxy phosphonates of this invention can be added generally include as feedstuffs a cellulosic roughage component such as hay, straw, plant hulls, corn cobs, etc. Protein-containing components such as whole grains, including corn, wheat, barley, oats, rye, millet and alfalfa are typically included.

The following examples illustrate compositions and methods used in the practice of this invention, but are not intended to be limiting thereof.

EXAMPLE I

Gelatin capsules are prepared by conventional methods, comprising as follows:

    ______________________________________                                         Ingredient          Mg per capsule                                             ______________________________________                                         EtCDP,Na.sub.5      350.0                                                      Starch              50.0                                                       ______________________________________                                    

The above capsules are administered twice daily to substantially increase glucose metabolism in diabetic patients having need of such treatment.

Similar results to those obtained with the capsules of Example I are secured when the EtCDP,Na₅ is replaced by an equivalent amount of EtCDP (free acid form), and the following carboxy phosphonates, respectively: EtCDP,Na₃ ; EtCDP,NH₄ Na₃ ; EtCDP,Li₂ ; EtCDP,dimethyl; EtCDP,K₃ ; EtCDP,K₂ Na₂ ; ethane-1,2-dicarboxy-1-hydroxy-1,2-diphosphonic acid; ethane-1,2-dicarboxy-1-chloro-1,2-diphosphonic acid; ethane-1,2-dicarboxy-1,2-dihydroxy-1,2-diphosphonic acid; and butane-1,2-dicarboxy-1,2-diphosphonic acid, respectively.

EXAMPLE II

Tablets are prepared by conventional methods, formulated as follows:

    ______________________________________                                         Ingredient           Mg per Tablet                                             ______________________________________                                         ECDP*                250.00                                                    Lactose              40.00                                                     Starch               2.50                                                      Magnesium stearate   1.00                                                      ______________________________________                                          *Ethene-1,2-dicarboxy-1-phosphonic acid                                  

The above composition is administered orally four times daily to increase glucose metabolism in a patient weighing approximately 70 kilograms, having a predisposition to carbohydrate intolerance.

Similar results are achieved with tablets formulated as above but replacing ECDP with monosodium ECDP, dipotassium ECDP, disodium, diammonium ECDP, tetrasodium ECDP, tetramethyl ECDP, ethane-2-carboxy-1,1-diphosphonic acid and hexane-2,2-dicarboxy-1,1-diphosphonic acid, respectively.

EXAMPLES III-VIII

The carboxy phosphonates can also be administered parenterally in aqueous solution by subcutaneous, intradermal, intramuscular or intravenous injection, or i.v. infusion. The usual, and preferred, dosage ranges by these modes of administration are as follows:

Subcutaneous: 0.05-10 mg/kg

Intradermal: 0.05-10 mg/kg

Intramuscular: 0.05-5 mg/kg

Intravenous: 0.05-5 mg/kg

Solutions for parenteral administration are prepared by dissolving the indicated carboxy phosphonic acids in distilled water at the specified concentration, adjusting the pH to 7.4 with the base corresponding to the indicated salt form, and sterilizing same by standard sterilization techniques.

    ______________________________________                                                                        Conc.                                           Ex.       Phosphonate          mg/ml                                           ______________________________________                                         III       EtCDP,K              10.0                                            IV        EtCDP,K.sub.2        15.0                                            V         EtCDP,Na.sub.2 + Na.sub.3  mixture                                                                   5.0                                            VI        EtCDP,Na.sub.5       25.0                                            VII       ECDP, Et ester       13.0                                            VIII      1-hydroxy-EtCDP      18.0                                            ______________________________________                                    

The solutions of the foregoing examples are administered by injection to animals (including humans) in an amount sufficient to provide desired dosage levels as hereinbefore specified to enhance carbohydrate metabolism. Preferably, the solutions are packaged in sealed ampules for single dosage hypodermic injections.

EXAMPLE IX

A complete feed composition embodying the present invention and useful for enhancing carbohydrate metabolism in animals is as follows:

    ______________________________________                                         Component            Parts by Weight                                           ______________________________________                                         Timothy hay          960                                                       Dehydrated alfalfa   40                                                        Yellow corn          600                                                       Corn starch          310                                                       Iodized salt         10                                                        Bone meal            20                                                        EtCDP (acid form)    40                                                        ______________________________________                                     

What is claimed is:
 1. A process for treating diabetes mellitus in humans and lower animals, comprising administering to a human or lower animal in need of such treatment a safe and effective amount of a pharmaceutically acceptable carboxy phosphonate compound which is a member selected from the group consisting of carboxy vicinal phosphonates, dicarboxy monophosphonates and carboxy geminal phosphonates.
 2. A process according to claim 1 wherein the carboxy phosphonate compound is a vic-dicarboxy, vic-diphosphonate compound.
 3. A process according to claim 2 wherein the vic-dicarboxy, vic-diphosphonate compound is ethane-1,2-dicarboxy-1,2-diphosphonate.
 4. A process according to claim 3 wherein the ethane-1,2-dicarboxy-1,2-diphosphonate is in the sodium salt form.
 5. A process according to claim 4 which employs pentasodium ethane-1,2-dicarboxy-1,2-diphosphonate. 